The present invention generally relates to an image forming arrangement and more particularly, to a copying apparatus capable of effecting a simultaneous multi-color copying control for obtaining images in a plurality of colors by causing a plurality of developing units to function through change-over during one copying operation.
Conventionally, there has been known a copying apparatus provided with a plurality of developing units, and so arranged to effect color-copying in a single color such as red, yellow or the like through selection of a developing unit to be used from said developing units for different colors.
With respect to the above, there has also been previously proposed a copying apparatus capable of effecting a simultaneous multi-color copying control for obtaining an image in a plurality of colors in one copy paper sheet by causing the plurality of developing units to function through change-over during one exposure operation in the application assigned to the same assignee as in the present invention. By the above simultaneous multi-color copying control, it is possible to copy left and right sides of an original document into images of different colors or to emphasize particular portions of an original document by using different colors thereat, even by one copying operation, and therefore, there are such advantages that, not only labor required for operation of the copying apparatus or for setting of the original document is reduced to half, but time necessary for the copying may be remarkably decreased.
However, in the copying apparatus capable of effecting the simultaneous multi-color copying control as referred to above, in the case where, for example, two developing units are provided to enable the simultaneous multi-color copying control in two colors, since both of the two developing units are used in the simultaneous multi-color copying mode, there is no room for selecting the developing units. Therefore, in this case, operation of a developing unit selecting key is insignificant. Moreover, in such a case, if it is so arranged to accept an input from the developing unit selecting key, there is such as inconvenience that, in spite of the fact that there is no alteration of the developing unit while the simultaneous multi-color copying mode is selected, undesirable change-over is automatically effected to the developing unit selected during the simultaneous multi-color copying mode when the normal mode is restored, with the simultaneous multi-color copying mode being released.
Therefore, different developing units are undesirably selected before and after selection of the simultaneous multi-color copying mode as the developing unit to be used for the normal mode, and if copying is effected without noticing such a state, there is a possibility that a miscopying takes place thereby.